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Description

tinyDriver is a breakout board for the Atmel ATtiny84 chip, which comes integrated with a motor driver chip and an RGB LED. The idea was to create a convenient platform that can be used to understand microcontrollers in depth, by studying the datasheet and making use of the various features of the chip such as timers, PWM, interrupts, ADC, and digital I/O.

This is an Open Source Hardware Project, and you can find more details here:

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This is an interesting project. One suggestion: in some cases one may want to measure the current fed through the driver (I'm reluctant to feed current to any motor without doing that). The poor man's option is to put a very small resistance in series with the ground return from the H-bridges and guess the load current knowing the switching state. I know this drops the efficiency of the bridge further and in this case may mess the voltage of the ground reference of the DRV8835 but if you find this feature of interest you may consider leaving a gap with a 0 ohm resistance and a few traces that may be used in case someone wants to use this.

"There is a weak pulldown resistor (approximately 100 kΩ) to ground on the input pins.

VCC and VM may be applied and removed in any order. When VCC is removed, the device enters a low powerstate and draws very little current from VM. To minimize current draw, keep the input pins at 0 V during sleepmode."

So at a 5V output on a pin, the 100K draws only 0.5 uA. I have been testing loading on all 5 pins with VCC jumper disconnected and so far it looks OK.

I am talking about internal ESD protection, not power down. If the part could handle signals without power applied, the maximum parameter would be written differently. They would given an actual voltage e.g. 5.5V. The +0.5V means a diode.

One thing you could do is to make sure that all those I/O pins are always driven low when you pull the jumper. If they are high, then the ESD diode would conduct.

Just using the power with AND gate can be tricky as the signal level isn't going to be well defined.

Or you an use 74LVC/AHC gates that are powered from the DRV8835 side of the jumper to buffer those signals. These 5V tolerant series are do not have the diodes to the VCC so they don't leak power thus they are designed to be use in situations like this.